Pin type porcelain insulators for high voltage transmission lines are mainly used to insulate and support conductors in high voltage overhead transmission lines. It is divided into five grades of 6 kV, 10 kV, 15 kV, 20 kV and 35kV according to the rated voltage. The pin insulator is composed of porcelain and steel pin (or screw sleeve), and the porcelain and steel pin (or screw sleeve) are glued together with Portland cement. The surface of porcelain parts is white or brown, and the surface of steel feet is hot-dip galvanized.